Process for painting a fibrous surface



Nov. 16, 1965 G. DoMANsKl PROCESS FOR PAINTING A FIBROUS SURFACE FiledOct. 2,4. 1961 ...ozool 2359. ...o

United States atent 3,218,191 PROCESS FOR PAINTING A FIBROUS SURFACEGeorge Domanski, Hudson, Ohio, assignor to The Glidden Company,Cleveland, Ohio, a corporation of Ghio Filed Det. 24, 1961, Ser. No.147,191 Claims. (Cl. 117-72) This invention relates to a process forpainting a fibrous surface, particularly a textured board-like structurewhich exposes silicate fibers such as mineral Wool, glass liber, andasbestos, and acoustical panels so coated.

The advantages of my invention over conventional techniques includeeconomical obliteration of the fiber structure and improve holdout ofthe paint due to a process of coating illustrated in the attached ligureof drawins, which figure is a plan view of a fibrous acoustic panelwhich has been coated in accordance with the invention and has portionsof the coating broken away to better illustrate the sequence of coatingoperations.

My improvement in the painting of a fibrous surface comprises applyingan aqueous solution of at least one anion selected from the groupconsisting of borates, sulfates, carbonates, phosphates, acetates,sultites, chlorides, and nitrates substantially uniformly to thesurface, then applying thereover an aqueous latex emulsion paintcontaining a minor compatible proportion of polyvinyl alcohol based onthe latex solids in the paint.

The anion in the undercoating appears to perform an extremely efiicientcoagulation of the latex paint subsequently applied. Advantageously, theanion is in the form of an aqueous solution for handling and drying,that is, in the form of a stable acid or salt solution such as asolution of borax, sodium carbonate, acetic acid, sodium sulfate, mono-,di, or trisodiurn phosphate, sodium chloride, sodium sulfite, aluminumsulfate, etc. By phosphates I mean to include the various acidphosphates, by carbonates the bicarbonates and sesquicarbonates, bysulfates the bisulfates, by sultes the bisultites, and by borates thetetraborates.

Preferably the anion is in the salt form for convenient uniformapplication to the fibrous surface. The preferred anion is thetetraborate anion for achieving desired rapid coagulation at the minimumdosage, and borax (Na2B4O7-10H2O) is the preferred salt for eliiciencyin the practice of my invention.

The advantageous solution strength of the borax is l-3%, preferably 21/2by weight in water because this can be dispensed readily fromconventional spray guns without tending to crystallize out and clog theguns. I have found such borax solution particularly effective for use inmy invention when the borax solution is applied to the brous structureat the substantially uniform rate of about 5 grams of borax solution persquare foot of fibrous surface, although I have used as little as 1.5grams of borax solution per square foot, and as high as 9 grams of boraxsolution per square foot with good results. With the other salts oracids it is necessary to use a substantially heavier dosage, e.g., 4-10times as much to obtain comparable results.

When the anion is applied in the precoating step, it is desirable to dryor at least partially dry the surface before applying the paint coatingto obtain the most practical and economic coagulation of the latexpaint. Suitably, in a production operation where the object to be coatedis being fed into oven for forced drying, I use at least seconds of suchdrying after the precoating and preferably 30 seconds to a minute beforeapplying the latex paint.

The aqueous latex emulsion paint is a conventional suspension of pigmentand film-forming compounded latex dosed with at least about 1/2 percentof polyvinyl alcohol ice based on the latex solids of the paint. Thuscompounded, the paint coacts with the prior anion deposit to achievefiber obliteration and holdout at very low application rate (e.g., 20-30grams of dried paint per square foot with a reectometer reading, Y, ofover 70% which is desired in the trade). Use of a substantially lowerproportion of polyvinyl alcohol slows down this rapid coagulation and isundesirable as the paint loses holdout. Use of more than a minorproportion of polyvinyl alcohol based on the latex solides in the painttends to give poor color stability and high water sensitivity to thefinish and is, therefore, undesirable. Preferably, for efficiency andeconomy in the process I use between about 1A. percent and about 20% ofpolyvinyl alcohol based on total latex solids in the paint.

The preferred film-forming latices for eticiency and economy arepolyvinyl acetate homopolymer latices, but virtually any film-forminglatex which is compatible with polyvinyl alcohol can also be used, e.g.,copolymer latices of polyvinyl acetate with vinyl stearato, acryliclatices such as methyl methacrylate, copolymer latices of polyvinylchloride with vinylidene chloride, neoprene latices, natural latex, andbutadiene-styrene latrices. However, the latter two emulsions aredistinctly inferior in my process to the poyvinyl acetate-containinglatices because of poor color retention, or sensitivity to light, oroverbaking in process.

The polyvinyl alcohol that I prefer to use is that commercially readilyavailable, e.g., having percent hydrolysis between -100 and viscosity inthe range of 4-65 centipoises in 4% water solution at 20 C. However, Ican use less highly hydrolyzed grades of polyvinyl alcohol for mypurposes, eg., those over 50% hydrolyzed, and those of a greater orlesser degree of polymerization, c g., viscosity 2-100 centipoises,provided they can be rendered compatible with the latex emulsion paint.

The prime use of my process is in coating acoustical panels with liatfinishes having low gloss readings. The panels can lhave a surface ofvegetable fiber such as paper, macerated bagasse, jute, etc., butusually present a silicate fiber surface that is diliicult to coateconomically. An advantageous practice in forming the panels is to sandthem smooth preparatory to coating, to cover them with a sheet of fiberglass mat -or asbestos paper, and then to apply my coating system. Theprefrred resulting film is discontinuous so sound absorption is notgreatly impaired. If a continuous film is obtained by an especiallyheavy application of paint, the panel can be perforated subsequent tocoating process to -obtain sound absorption. The panel is backed in anover, e.g., 300-400 F. for 1.5-3 minutes. When a borax solution is usedin the precoating, I have found that the panels resist color degradationfrom overbaking (being left too long in the oven). The borax-treatedboards also have a desirably low iiarne spread rating.

Unless otherwise indicated all parts are parts by weight and allpercentages are weight percentages in this application.

F or the following example a white paint was made by mixing togetherparts of pigmentary anatase titanium dioxide, 400 parts of fine calciumcarbonate, 400 parts of ne calcium silicate, 11 parts of tricresylphosphate, r560 parts of water, 200 parts of an aqueous polyvinylacetate homopolymer emulsion having viscosity of 900- 1300 centipoises,1-3 micron particle sizes 54% resin solids, pH of 4-6 and weight pergallon of 9.23 lbs. at 25 C., and 50 parts of a 10% solution ofpolyvinyl alcohol in water, the polyvinyl alcohol being 981/2-100%hydrolyzed and exhibiting viscosity between 22-32 centipoises in 4%aqueous solution at 60 F.

In place of the white paint so made colored mineral 3 pigments orconventional organic tinting agents such as phthalocyanine colors couldbe employed to give a colored paint.

Example A 21/2% by Weight aqueous solution of borax (Na2B4O7-l0l-I2O)was made up and sprayed on a mineral Wool acoustical board overlaid witha sheet of textured asbestos paper that exhibited a coarse ibrousStructure, the borax solution dosage being 5 grams per square foot. Theso-treated board was permitted to ashevaporate water for about 30seconds in an oven maintained at 350 F. Then the treated board wassprayed with the white latex paint in a single thin coat and dried for 3minutes in the oven at 350 F. The dry weight of paint applied was 20-25grams per square foot of boaad A discontinuous flat 'film resulted. 1tcompletely obliterated the fiber structure of the board. r)The soundabsorption of the board was not greatly impaired, that is, the boardretained about 70% of its original noise-reduction coe-icient. Patterndefinition on the painted surface was excellent.

I claim:

1. In the painting of a fibrous surface Whose fibers are selected fromthe group consisting of vegetable fibers and silicate fibers, theimprovement which consists of (A) applying an aqeuous solutionconsisting essentially of Water and dissolved salt, the latterprovidingJ at least one anion selected from the group consisting7 ofborates, sulfacts, carbonates, phosphates, acetates, sultes, clhoridesand nitrates to said fibrous surface in an emulsion-coagulating amountwhich for the tetraborate anion corresponds to between about 1.5 and 9grams of 1-3 weight percent aqueous borax solution per square foot ofbrous sur- 41 face and for all other anions of said group is about fi-10times greater, and (B) thereafter applying7 to said surface, with rapidcoagulation thereof into a discontinuous film, an aqueous latex emulsionpaint having `cornpatibly blended therewith between about 0.5 and 20% byWeight of polyvinyl alcohol, based on the latex solids of said paint.

2. The process as claimed in claim 1 and wherein the process includesthe step of at least partially drying the applied anion solution beforesaid polyvinyl-alcoholmodified emulsion paint is applied.

3. The process as claimed in claim 2 wherein the applied aqueous saltsolution is a 1-3% aqueous solution of borax, by weight.

4. The process as claimedin claim 3 wherein the emulsion paint containsa vinyl acetate polymer latex.

5, The process as claimed in claim 1 wherein the anion is thetetraborate anion of boraX.

References Cited by the Examiner UNITED STATES PATENTS 113416589 5/1931Espig et al. 117-123 2,251,296 8/1941 Shipp 117-161 2,542,428 2/1951Peik 117-70 2,562,711 7/1951 Gessler et al. 171--33 XR 2,591,90A 4/1952Zola 10G-170 2,722,489 11/1955 Hennessey et al. 117-126 2,855,32710/1958 Gilchrist et al. 117-140 2,941,899 6/1960 Stalego 117-72 XRWlLLlAM D. MARTN, Primary Examiner.

RCHARD D. NEVIUS, Exczrliner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent NO.3,218,191 November 16, 1965 George Domansk l It s hereby certified thaterror appears in the above numbered patent requiring correction and thatthe said Letters Patent should read as corrected below.

Column 1, line 16, for "drawns" read drawings Column Z, line 23, for"latrces" read 1atices line 45, for "prefrred" read preferred line 50,for "backed in an over" read baked in an oven column 3, line 15, for"boaad" read board lines 28 and Z9, for "sulfacts" read sulfates line29, for "clhordes" read chlorides Signed and sealed this 6th day ofSeptember 1966.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attestng Officer Commissioner ofPatents

1. IN THE PAINTING OF A FIBROUS SURFACE WHOSE FIBERS ARE SELECTED FROMTHE GROUP CONSISTING OF VEGETABLE FIBERS AND SILICATE FIBERS, THEIMPROVEMENT WHICH CONSISTS OF (A) APPLYING AN AQUEOUS SOLUTIONCONSISTING ESSENTIALLY OF WATER AND DISSOLVED SALT, THE LATTER PROVIDINGAT LEAST ONE ANION SELECTED FROM THE GROUP CONSISTING OF BORATES,SULFACTS, CARBONATES, PHOSPHATES, ACTATES, SULFITES, CLHORIDES ANDNITRATES TO SAID FIBROUS SURFACE IN AN EMULSION-COAGULATING AMOUNT WHICHFOR THE TETRABORATE ANION CORRESPONDS TO BETWEEN ABOUT 1.5 AND 9 GRAMSOF 1-3 WEIGHT PERCENT AQUEOUS BORAX SOLUTION PER SQUARE FOOT OF FIBROUSSURFACE AND FOR ALL OTHER ANIONS OF SAID GROUP IS ABOUT 4-10 TIMESGREATER, AND (B) THEREAFTER APPLYING TO SAID SURFACE, WITH RAPIDCOAGULATION THEREOF INTO A DISCONTINUOUS FILM, AN AQUEOUS LATEX EMULSIONPAINT HAVING COMPATIBLY BLENDED THEREWITH BETWEEN ABOUT 0.5 AND 20% BYWEIGHT OF POLYVINYL ALCOHOL, BASED ON THE LATEX SOLIDS OF SAID PAINT.